Many LED chips of today are mounted on a ceramic substrate comprising mounting contacts and supply tracks for electrically driving the LED chip. The LED substrate package is usually soldered or glued to a Printed Circuit Board (PCB) for electrical connection to the contacts and supply tracks, and for thermal connection to the heat sink of a light emitting assembly. The mounting substrate is often of a high density polycrystalline ceramic having a relatively high thermal conductivity but relatively poor light reflectivity. A known measure for increasing the reflectivity of the ceramic is to increase the porosity of the ceramic. However, this simultaneously reduces the thermal conductivity considerably.
An attempt to solve these problems is provided in WO 2009/075530 disclosing a semiconductor package having LED-chips mounted on electrodes, which are arranged on a substrate. On top of the substrate, and next to the electrodes is provided a reflective coating comprising titanium dioxide, TiO2, and a silicone binder. In order to achieve a reflective coating on top of the substrate and not on the electrodes, WO 2009/075530 proposes using a mask to protect the electrodes. However, this method appears to be complicated and time consuming, since it involves aligning a mask with the electrodes.